PO Box 296 Olinda Vic 3788 April 2020 http://www.rhododendron.com.au Newsletter of the ARSV The “tschonoskii” rhododendrons Our attraction to rhododendrons and allied plants is surely their spectacular flowers but there are many species that are not magnificent flowerers nor spectacular plants. They may thus be of limited horticultural interest but are, nonetheless, fascinating in their own right. One such group is the “tschonoskii alliance” a group of Tsutsui azaleas from Japan, Korea and neighboring Russia which includes R. tschonoskii R. tsusiophyllum, R. trinerve and R. tetramerum. These are all small shrubs that grow on wooded mountain sides as well as on exposed rocky sites and cliffs. They bear very small white flowers and have small leaves. As usual, the naming and taxonomy is open to argument. Davidian treats R. trinerve as a subspecies of tschonoskii, and makes no mention of R. tetramerum while Cox’s Encyclopedia of Rhododendron Species only mentions R. tschonoskii and R. tsusiophyllum. The Plant List includes all as species with unresolved names. A group of Japanese and Korean botanists have been researching this group and have not only more definitely sorted this group out but have also discovered a new species R. sohoyakiense and two new varieties - R. s. kiusianum from Kyushu and R. s. koreanum from South Korea. The nominate R. s. sohoyakiense is from Shikoku and southern Honshu. These findings were based on detailed analysis of the morphology of the plants and analysis of DNA. As the photographs show they are small shrubby plants and it may be hard to distinguish between the species. Yoichi et al. (2019) provide a key to identify them but it could still be difficult. Cox notes that R. tschonoskii, and presumably the other species, is almost deciduous and produces orange red to reddish brown foliage in autumn. He also says that R. tsusiophyllum forms a “dainty little creeping or mound-forming shrub”. These are hardy species and can take the cold as well as the hot Australian summers. 1 R. tsusiophyllum is a bit different to the others. It has anthers that open by a longitudinal slit rather than by a pore at the top that all other Rhododendrons have. It was originally described in its own genus Tsusiophyllum tanakae. DRBG has a R. tschonoskii which has been in the gardens for probably 40 years. We have checked its identity using the keys in Yoichi et al. and it appears to be R. tschonoskii rather than one of the other species. It has survived decades of neglect and we have propagated from it as it appears to be the only one in the gardens. Reference: Yoichi, W., Minamitani, T., Oh, SH., Nagano, A. J., Abe, H. and Yukawa, T. 2019. New taxa of Rhododendron tschonoskii alliance (Ericaceae) from East Asia. PhytoKeys 134: 97–114 (2019).doi: 10.3897/phytokeys.134.38216. Committee John O'Hara President [email protected] 03 9593 1323 Graham Price [email protected] 0409 639 448 Andrew Rouse Vice-President [email protected] 0424 750 406 Peter Grose [email protected] 04 8877 3577 Michael Hare Secretary [email protected] 0405 403 607 Dan Macleod [email protected] 0400 594 319 Prue Crome Treasurer [email protected] 0419 659 741 Alex Pottage [email protected] 03 5786 1595 Francis Crome Newsletter editor [email protected] 0417 730 291 Walter Lobbezoo Librarian [email protected] 03 9751 1704 2 Photographs and credits 3 No. 1 - R. sohoyakiense. sohoyakiense variety (photo from Yoichi et al. 2019) No.2 - R. trinerve photographed by Qwert1234 on Mt Mikuni-dake, Fukushima pref., Japan (https://species.wikimedia.org/wiki/Rhododendron_ tschonoskii_subsp._trinerve#/media/File:Rhododend ron_ tschonoskii_subsp._trinerve.JPG0) No 3 - R. tsusiophyllum photographed by Knud Petersen of the Danish chapter of the ARS. (http://www.rhododendron.dk/tsusiophyllum.html) No 4 - R. tschonoskii photographed on Mt Adatara by “user Σ64” (https://commons.wikimedia.org/wiki/ File:Rhododendron_tschonoskii_05 No. 5 R.tschonoskii in the DRBG. 4 5 Rhododendron in focus: Rhododendron augustinii Section Triflora This species is regarded as the best blue in the Rhododendron genus. It comes from Sichuan and Hubei in Northern China at 1200 to 3400 metres, generally in open rocky locations. A check of our database shows about 150 R. augustinii have been planted in the garden, many of these in the largely inaccessible area along the Mathias Road boundary. However, a review of the plants in the Triflora bed revealed that there are 12 plants of various forms of this species. At present this area looks untidy with long grass and weeds proliferating, but the plants, which are around 50 years old, look surprisingly healthy and are two to three metres high. They are an important part of our species collection. The most impressive plant of augustinii I have seen was in the garden of Norm and Jill Brown of Ferny Creek, which we visited in October last year. This plant was growing on a steep slope and is around three metres high, covered in violet-blue flowers. (bottom photo). The top photo shows R. augustinii at DRBG with R. yunnanense alongside. Alan Kepert Vireyas in the garden right now and some garden jobs If you have the right spot vireyas make great garden plants. These are some flowering in Prue Crome’s garden in Kallista right now. She keeps them tight and flowering well by constant judicious pruning. They like living under tree ferns. Autumn is on us and now is a good time to clean up our Rhododendrons in the garden and prepare for spring. It is a good idea to clear away mulch and debris from the stems so as to reduce the chance of rot in winter and clean up any dead branches or flower heads if you have not done so already. Clockwise from top: Carringtonia hybrid, Saxifragoides hybrid, Great Scent-sation, Kisses. .